.nav{
    width: 100%;
    height: 100px;
    display: flex;
}
.leftbox{
    width: 50%;
    height: 539px;
    float: left;
    background-color: red;
}
.rightbox{
    width: 50%;
    height: 539px;
    float: left;
    background-color: pink;
}
/* .top-app{
    display: flex;
    justify-content: space-around;
} */
